KR20160032664A - All solid lithium ion secondary battery - Google Patents

Abstract

Provided is an all solid lithium ion secondary battery. The all solid lithium ion secondary battery has a positive electrode active material particle and a positive electrode including a solid electrolyte particle which comes into contact with the positive electrode active material particle, wherein the positive electrode active material particle comprises: a lithium cobalt oxide particle; a first coating layer which includes a nickel element, and covers at least one portion of the lithium cobalt oxide particle; and an M1 element, and a composition of the positive electrode active material particle is represented by chemical formula 1. The average diameter of the positive electrode active material particle has 5 to 35 μm. The all solid lithium ion secondary battery can improve discharge capacity and cycle properties.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a high-

The present invention relates to a reactor-type lithium ion secondary battery.

Since the lithium ion secondary battery has a large charge / discharge capacity, a high operation potential and an excellent charge / discharge cycle characteristic, it can be used as a portable information terminal, a portable electronic device, a small power storage device for home use, a motorcycle powered by a motor, Demand for applications such as automobiles is increasing. In the lithium ion secondary battery, a nonaqueous electrolyte solution in which a lithium salt is dissolved in an organic solvent as an electrolyte is used. However, such nonaqueous electrolyte has a problem of safety in terms of ease of ignition and leakage of the electrolyte. Therefore, recently, in order to improve the safety of the lithium ion secondary battery, research on a high-voltage lithium ion secondary battery using a solid electrolyte made of an inorganic material, which is a non-combustible material, has been actively conducted.

As a solid electrolyte of a lithium ion secondary battery, a sulfide or an oxide can be used, but a sulfide-based solid electrolyte is the most expected material from the viewpoint of lithium ion conductivity. However, when a sulfide-based solid electrolyte is used, a reaction occurs at the interface between the positive electrode active material particle and the solid electrolyte particle at the time of charging, and this interface resistance component is generated so that when the lithium ion moves through the interface between the positive electrode active material particle and the solid electrolyte particle (Hereinafter also referred to as " interfacial resistance ") is likely to increase. This increase in interfacial resistance lowers the lithium ion conductivity, which causes a problem that the output of the reactor-type lithium ion secondary battery is lowered.

Because of the above problems, it has been possible to use a positive electrode active material particle containing Ni as a positive electrode active material particle of a high-voltage lithium ion secondary battery, for example, nickel cobalt lithium manganese oxide (hereinafter also referred to as "NCM"), nickel cobalt aluminum ) Particles have been used. This is because the positive electrode active material particles containing Ni are difficult to generate a resistance component between the sulfide-based solid electrolytes.

On the other hand, LiCoO ₂ (hereinafter also referred to as "LCO") particles are known as positive electrode active material particles used in nonaqueous lithium ion secondary batteries. LCO particles are more dense than NCM particles and NCA particles.

In addition, the lithium ion diffusion rate of NCM particles and NCA particles is small. Therefore, when NCM particles and NCA particles are used as the cathode active material particles, it is necessary to reduce the primary particles of the NCM particles and the NCA particles, and to agglomerate (i.e., secondaryize) these primary particles. If the primary particles are large, it takes a long time for the lithium ions to rotate around the whole particle and the cycle characteristics of the lithium ion secondary battery are lowered. Therefore, a large number of voids are formed between the cathode active material particles in the cathode active material layer having NCM particles and NCA particles as cathode active material particles. That is, the filling property of the positive electrode active material particles is low. In contrast, the lithium ion diffusion rate of the LCO particles is larger than the lithium ion diffusion rate of the NCM particles and the NCA particles, so that they can be used as the primary particles. Therefore, the filling property of the positive electrode active material is enhanced.

For this reason, when the LCO particles are used as the cathode active material particles, the density (bulk density) of the cathode active material layer can be increased. Therefore, there is a demand for use of LCO particles in high-electron type lithium ion secondary batteries.

However, when the LCO particles are used as the cathode active material particles of the lithium ion secondary battery, the above-mentioned interfacial resistance is remarkably increased, and as a result, the discharge capacity and the cycle characteristics are remarkably lowered. Thus, it has been proposed to coat the surface of the positive electrode active material particles with LiNbO ₃ , Li ₄ Ti ₅ O _12, Al compound, or the like. However, even with this technique, satisfactory values for discharge capacity and cycle characteristics could not be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a lithium ion secondary battery capable of using LCO particles as cathode active material particles and also capable of improving the discharge capacity and cycle characteristics of a lithium- Thereby providing a secondary battery.

In order to solve the above problems, according to an aspect of the present invention,

1. A lithium ion secondary battery comprising a positive electrode active material particle and a positive electrode including solid electrolyte particles in contact with the positive electrode active material particle, wherein the positive electrode active material particle comprises lithium cobalt oxide (LCO) particles and nickel (Ni) A first coating layer covering at least a part of the lithium cobalt oxide particles and a second covering layer covering at least a portion of the lithium cobalt oxide particles; There is provided a lithium ion secondary battery comprising at least one element M1 selected from the group consisting of Mo, Ru, In, Sn, Sb, La, Ce, Pr, Eu, Tb, Hf, Ta and Pb.

According to one embodiment, the element M1 may be at least one or more elements selected from the group consisting of Mg, Al, and Mn.

According to one embodiment, the first coating layer may further include at least one or more elements selected from the group consisting of a lithium atom, an oxygen atom and the same element as the element M1.

The total composition of the cathode active material particles may be represented by the following formula (1).

[Chemical Formula 1]

Li _x Ni _y Co _z M1 _{1- y z} O ₂

In the above formula (1)

M1 is the element M1, and x, y, z, and a satisfy 0.5 <x <1.2, 0 <y <0.4, z> 0.6, and y + z? 1.0.

According to one embodiment, the average particle size of the cathode active material particles may be 5 to 35 μm.

According to one embodiment, the molar ratio of the nickel atoms to the cobalt (Co) atoms in the cathode active material particles may be continuously changing from the surface of the cathode active material particle toward the center.

According to one embodiment, the element M1 may be included in the LCO particles.

According to one embodiment, the cathode active material particles further include a second coating layer covering at least a part of the first coating layer, and the second coating layer may be formed of B, Mg, Al, Si, Sc, Ti, V, Cr, Mn, Fe At least one element M2 selected from the group consisting of Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, In, Sn, Sb, La, Ce, Pr, Eu, Tb, Hf, .

According to one embodiment, the element M2 may be at least one element selected from the group consisting of Al, Ti, Ga, Y, Zr, Nb, In, La and Ce.

According to one embodiment, the molar ratio of the element M2 to the total number of atoms of the total transition metal of the cathode active material particles may be 10.0 mol% or less.

 According to one embodiment, the cathode active material particles may be approximately spherical.

According to one embodiment, the solid electrolyte particles may be sulfide-based solid electrolyte particles.

According to one embodiment, the sulfide-based solid electrolyte particle includes at least sulfur and lithium, and at least one of phosphorus (P), silicon (Si), boron (B), aluminum (Al), germanium (Ge) , Gallium (Ga), indium (In), and a halogen element.

According to the present invention, LCO particles can be used as the cathode active material particles, and the discharge capacity and cycle characteristics of the high-voltage lithium ion secondary battery can be improved.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory diagram schematically showing a configuration of a lithium ion secondary battery according to one embodiment; FIG.
2 is an explanatory diagram schematically showing a configuration of a cathode active material particle according to one embodiment.
3 is an explanatory diagram schematically showing a modified example of the anode layer.
4 is an explanatory diagram schematically showing a configuration of a cathode active material particle according to the modified example.
5 is a view of HAADF-STEM (high-angle scattering cyclic obscuration night transmission microscope) of the cross section of the cathode active material particles obtained in Example 3. Fig.
6 is a graph (intensity line profile) showing the correlation between the depth of the cathode active material particles obtained in Example 3 on the sample surface and the surface density (atomic%) of each element (O, Co, Ni).
7 is an explanatory view showing an increase in interfacial resistance of a conventional high-tension lithium ion secondary battery.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description and drawings, constituent elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant description will be omitted.

<1. Problems in using a solid electrolyte>

First, referring to Fig. 7, a problem in the case of using a solid electrolyte will be described. 7 is an explanatory view showing a schematic configuration of a conventional lithium ion secondary battery 100 (hereinafter also referred to as &quot; lithium ion secondary battery 100 &quot;).

The lithium ion secondary battery 100 has a structure in which the anode layer 110, the cathode layer 120, and the solid electrolyte layer 130 are laminated. The anode layer 110 is composed of mixed particles in which the cathode active material particles 111 and the sulfide-based solid electrolyte particles 131 (hereinafter also referred to as &quot; solid electrolyte particles 131 &quot;) are mixed. Likewise, the negative electrode layer 120 is composed of mixed particles in which the negative electrode active material particles 121 and the solid electrolyte particles 131 are mixed. The solid electrolyte layer 130 is provided between the anode layer 110 and the cathode layer 120. The solid electrolyte layer 130 is composed of solid electrolyte particles 131.

Since the lithium ion secondary battery 100 using the sulfide-based solid electrolyte has a solid state of the cathode active material and the electrolyte, it is more difficult for the electrolyte to permeate the inside of the cathode active material than in the case of using the organic electrolytic solution as the electrolyte, It is difficult to sufficiently secure the movement path of lithium ions and electrons since the area is likely to decrease. 4, the anode layer 110 is composed of mixed particles of the cathode active material particles 111 and the sulfide-based solid electrolyte particles 131, and the anode active material particles 121 and the sulfide-based solid electrolyte particles 131 ) Are mixed with each other to constitute the cathode layer 120. This increases the area of the interface between the active material and the solid electrolyte.

However, as described above, a reaction occurs at the interface between the positive electrode active material particle 111 and the solid electrolyte particle 131 at the time of filling, and the high-resistance layer 150 is formed. Specifically, the high-resistance layer 150 is formed by a reaction (side effect) between a transition metal element present on the surface of the cathode active material particle 111, oxygen (element) and a sulfur element present on the surface of the solid electrolyte particle 131, Lt; / RTI &gt; Here, the &quot; high resistance layer 150 &quot; is a layer made of a resistance component formed at the interface between the positive electrode active material particles 111 and the solid electrolyte particles 131, and is a layer of the positive electrode active material particles 111 and the sulfide- Quot; means a layer in which the resistance when lithium ions move is larger than that of lithium ions. Therefore, the interface resistance between the positive electrode active material particles 111 and the solid electrolyte particles 131 is easily increased. If the area of the interface between the positive electrode active material particles 111 and the solid electrolyte particles 131 is increased, the movement path of lithium ions and electrons can be ensured while the high resistance layer 150 is easily formed. Therefore, the movement of lithium ions from the positive electrode active material particles 111 to the solid electrolyte particles 131 is inhibited by the high resistance layer 150. As a result, since the lithium ion conductivity is lowered, the output of the lithium ion secondary battery 100 is lowered.

Due to the above problems, cathode active material particles containing Ni, for example, NCM particles and NCA particles have been used as cathode active material particles of a lithium ion secondary battery in the past. Because the positive electrode active material particles containing Ni are difficult to generate a resistance component between the sulfide-based solid electrolytes.

On the other hand, LCO particles are known as positive electrode active material particles used in nonaqueous lithium ion secondary batteries. When the LCO particles are used as the positive electrode active material particles of the non-aqueous lithium ion secondary battery, the density (bulk density) of the positive electrode active material layer can be increased. For this reason, there is a demand for use of LCO particles in high-reactor type lithium ion secondary batteries.

However, when the LCO particles are used as the cathode active material particles of the lithium ion secondary battery 100, the interfacial resistance by the high resistance layer 150 described above remarkably increases, and as a result, the discharge capacity and the cycle characteristics There was a problem in which it significantly deteriorated. Thus, a method of coating the surface of the cathode active material particles with LiNbO ₃ , Li ₄ Ti ₅ O _12, Al compound, or the like has been proposed. However, even with this technique, satisfactory values for discharge capacity and cycle characteristics could not be obtained.

<2. Examination according to the present invention>

Therefore, the present inventors have studied the technique for suppressing the formation of the high-resistance layer (150). As a result, the present inventor conceived of coating LCO particles with nickel atoms. Nickel atoms are difficult to generate the high-resistance layer 150 between the sulfide-based solid electrolytes. Further, the inventor of the present invention has conducted further studies on coated particles. As a result, the present inventor contemplated introducing more specific elements M1 and M2 into the coated particles. Examples of the introduction form of the element M1 include a method in which the element M1 is contained (coated) in the coated particles. As the introduction form of the element M2, the coated particle is further coated with the element M2. According to the results of the above research, the inventor of the present invention has made the above-mentioned high-tension lithium ion secondary battery according to the present embodiment. Hereinafter, the lithium ion secondary battery according to the present embodiment will be described in detail.

<3. Configuration of Lithium Ion Secondary Battery>

Next, the configuration of a lithium ion secondary battery according to a preferred embodiment of the present invention will be described in detail with reference to Fig. 1 is an explanatory diagram schematically showing a configuration of a lithium ion secondary battery 1 according to the present embodiment.

1, the lithium ion secondary battery 1 according to the present embodiment is a high-voltage lithium ion secondary battery and includes an anode layer 10, a cathode layer 20, an anode layer 10, and a cathode layer 20 And a solid electrolyte layer 30 interposed therebetween.

(3.1. Anode layer (10)

The anode layer 10 includes mixed particles in which the coated particles 10a and the solid electrolyte particles 31 are mixed. The coated particles 10a include the positive electrode active material particles 11 and the second coating layer 12 as shown in Fig.

(3.1.1 cathode active material particle 11)

The positive electrode active material particle 11 includes LCO particles 11a and a first coating layer 11b. The LCO particles (11a) are particles composed of LCO. The shape of the LCO particles 11a is substantially spherical. The LCO particles 11a may contain a component that is inevitably incorporated into the LCO particles 11a at the time of manufacturing the covered particles 10a. For example, when the precursor of the first coating layer 11b is fired, nickel atoms migrate from the first coating layer 11b to the LCO particles 11a. Thus, the LCO particles 11a may contain nickel atoms.

In addition, the LCO particles 11a may comprise (i.e., may employ) an element M1. The element M1 is an element selected from B, Mg, Al, Si, Sc, Ti, V, Cr, Mn, Fe, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, In, Sn, Sb, , Eu, Tb, Hf, Ta, and Pb. The element M1 may be at least one or more elements selected from the group consisting of Mg, Al, and Mn, for example. The content of the element M1 is 10 mol% or less with respect to the number of moles of the cobalt atoms contained in the LCO and is determined so as to satisfy the following formula (1).

The first coating layer 11b covers at least a part of the surface of the LCO particles 11a. The first coating layer 11b contains at least nickel atoms. The first coating layer 11b may also contain at least one or more of lithium atom, oxygen atom and element M1. The content of the nickel atom, the lithium atom and the element M1 and the molar ratio thereof can be determined so as to satisfy the following formula (1).

The composition of the whole positive electrode active material particle 11 may be represented by the following formula (1).

[Chemical Formula 1]

Li _x Ni _y Co _z M1 _{1- y z} O ₂

In the formula (1), M1 is the above-mentioned element M1, and x, y and z are values satisfying 0.5 <x <1.2, 0 <y <0.4, z> 0.6 and y + z? 1.0.

The average particle diameter of the positive electrode active material particles 11 is 5 to 35 占 퐉. Here, the particle size of the cathode active material particle 11 is a particle diameter when the cathode active material particle 11 is regarded as a sphere. The average particle diameter is the particle size D50 (median diameter) of the cathode active material particle 11. The discharge capacity and cycle characteristics of the lithium ion secondary battery 1 may be lowered when the average particle size of the cathode active material particles 11 is less than 5 占 퐉 and when the average particle diameter is more than 35 占 퐉.

Here, the average particle diameter of the cathode active material particle 11 can be measured by a dry particle size distribution measuring apparatus (for example, Microtrack MT-3000II, Nikkiso Co., Ltd.). In the following examples, the average particle diameter of the cathode active material particles 11 and the like was measured using this apparatus.

The positive electrode active material particles 11 may be substantially spherical. In this case, the discharge capacity and cycle characteristics of the reactor-type lithium ion secondary battery 1 can be further improved.

The molar ratio of the nickel atoms to the cobalt atoms in the positive electrode active material particles 11 can continuously change from the surface of the positive electrode active material particles 11 toward the center thereof. Specifically, the surface density (number of atoms per unit area) of nickel atoms can be made smaller as the distance from the surface of the positive electrode active material particle 11 (or coated particle 10a) to the measurement surface becomes longer. On the other hand, the surface density of the cobalt atoms can be increased as the distance from the surface of the cathode active material particle 11 (or coated particle 10a) to the measurement surface increases. Such a change may occur at the interface between the LCO particles 11a and the first coating layer 11b and in the vicinity thereof.

(3.1.2. Coating layer (12)

The second coating layer 12 covers at least a part of the surface of the first coating layer 11b. The second coating layer 12 includes at least the element M2. The element M2 is at least one element selected from B, Mg, Al, Si, Sc, Ti, V, Cr, Mn, Fe, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, In, Sn, Sb, , Eu, Tb, Hf, Ta, and Pb. The element M2 may be at least one or more elements selected from the group consisting of Al, Ti, Ga, Y, Zr, Nb, In, La and Ce.

The molar ratio of the element M2 to the total number of atoms (total number of moles) of the total transition metal (for example, nickel atom and cobalt atom) of the positive electrode active material particle 11 may be 10.0 mol% or less. Further, the second coating layer 12 may contain at least one or more of lithium atom and oxygen atom. By covering the cathode active material particles 11 with the second coating layer 12 having the above composition, the discharge capacity and cycle characteristics of the lithium ion secondary battery 1 can be further improved. The lower limit of the molar ratio of the element M2 is not particularly limited, but may be, for example, 0.1 mol%. In this case, the discharge capacity and cycle characteristics can be further improved.

Since the coated particles 10a have the above structure, the reaction (side effect) between the sulfur element in the solid electrolyte particles 31 and the transition metal element in the cathode active material particle 11 is suppressed, The discharge capacity and cycle characteristics of the battery 1 can be improved.

The reason why the first coating layer 11b and the second coating layer 12 are formed on the surface of the LCO particle 11a is that the contrast of the cathode active material particle 11 due to the structural difference of the coating layer 12 (FE-SEM) and Transmission Electron Microscopy (TEM) image analysis using a differential scanning electron microscope (SEM). In the following embodiments, the structure of the cathode active material particle 11 was confirmed by HAADF-STEM.

(3.1.3 Other additives)

The anode layer 10 may contain not only the cathode active material particles 11 but also additives such as a conductive agent, a binder, an electrolyte, a filler, a dispersant, and an ion conductive agent appropriately selected and contained.

Examples of the conductive agent include graphite, carbon black, acetylene black, ketjen black, carbon fiber and metal powder. Examples of the binder include polytetrafluoroethylene, polyvinylidene fluoride, polyethylene And the like. Examples of the electrolyte include a sulfide-based solid electrolyte described later. In addition, as the filler, dispersant, ionic charge precursor and the like, conventionally known materials used for electrodes of lithium ion secondary batteries can be used.

(3.1.4. The anode layer 10 Variation example )

Fig. 3 shows a modified example of the anode layer 10. 3, the anode layer 10 according to the modification includes the cathode active material particles 11 and the solid electrolyte particles 31. [ The positive electrode active material particles 11 are obtained by removing the second coating layer 12 from the above-mentioned coated particles 10a as shown in Fig. As shown in the embodiments described later, discharge capacity and cycle characteristics can be improved in this modified example as well.

(3.2. Cathode layer (20)

(3.2.1 anode active material particle (21))

The negative electrode active material particles 21 contained in the negative electrode layer 20 according to the present embodiment are not particularly limited as long as they are materials capable of reversibly intercalating and deintercalating lithium or lithium.

Examples of the anode active material particles 21 include a lithium metal, a metal capable of alloying with lithium, a transition metal oxide, a non-transition metal oxide, a material capable of doping and dedoping lithium, Or more.

The lithium-alloyable metal may be selected from the group consisting of Si, Sn, Al, In, Ge, Pb, Bi, , A rare earth element or a combination element thereof and not Si), an Sn-Y alloy (Y is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, Or the like). The element Y may be at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Se, Te, Po, or a combination thereof.

The transition metal oxide may be, for example, tungsten oxide, molybdenum oxide, titanium oxide, lithium titanium oxide, vanadium oxide, lithium vanadium oxide, and the like.

The non-transition metal oxide may be, for example, SnO ₂ , SiO _x (0 <x <2) or the like.

Examples of the material capable of doping and dedoping lithium include Si, SiO ₂ , Si-Y alloy, Sn, SnO ₂ , Sn-Y alloy (where Y is an alkali metal, an alkaline earth metal, A Group 12 element, a Group 13 element, a Group 14 element, a Group 15 element, a Group 16 element, a transition metal, a rare earth element, or a combination element thereof, but not Sn). The element Y may be at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Se, Te, Po, or a combination thereof.

The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. Examples of the carbon-based material include natural graphite, artificial graphite, graphite carbon fiber, resin fired carbon, pyrolytic vapor grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin fired carbon, polyacene, Vapor grown carbon fiber, soft carbon or hard carbon, mesophase pitch carbide, or the like can be used. These may be used alone as the negative electrode active material 201, or may be used by mixing two or more thereof.

The carbon-based material may be amorphous, plate-like, flake, spherical, fibrous, or a combination thereof.

These negative electrode active material particles 21 may be used alone, or two or more thereof may be used together.

(2.2.2. Other additives)

The negative electrode layer 20 may contain additives such as a conductive agent, a binder, an electrolyte, a filler, a dispersing agent, and an ion conductive agent appropriately selected and contained in addition to the particles of the negative electrode active material particles 21. Specific examples of such materials include the same materials as the above-described anode layer 10.

(3.3 solids Electrolyte layer (30)

The solid electrolyte layer 30 according to the present embodiment includes the solid electrolyte particles 31. The solid electrolyte particles 31 may be sulfide-based solid electrolyte particles.

For example, the solid electrolyte particles 31 are sulfide solid electrolyte particles, which contain at least sulfur and lithium, and contain phosphorus (P), silicon (Si), boron (B), aluminum (Al), germanium And may further include at least one selected from zinc (Zn), gallium (Ga), indium (In), and halogen elements. It is known that the solid electrolyte particles 31, that is, the sulfide-based solid electrolytes satisfying these conditions are higher in lithium ion conductivity than inorganic compounds having different lithium ion conductivities. Specific examples of the solid electrolyte particles 31 include Li ₂ S and P ₂ S ₅ . Other examples include SiS ₂ , GeS ₂ , B ₂ S ₃ , and the like. The sulfide solid electrolyte may further contain Li ₃ PO ₄ , a halogen, a halogen compound, LISICON, LIPON (Li ₃ PO ₄ , Li ₂ PO ₄ ), or the like, to an inorganic solid electrolyte consisting of a combination of Li ₂ SP ₂ S ₅ , SiS ₂ , GeS ₂ , B ₂ S ₃ , _{+ y} PO _4-x N _x ), Thio-LISICON (Li _3.25 Ge _0.25 P _0.75 S ₄ ), Li ₂ O-Al ₂ O ₃ -TiO ₂ -P ₂ O ₅ (LATP) Can be used. They may be mixed and used. Li ₃ PO ₄ , a halogen, a halogen compound or the like may be added to the solid electrolyte particle 31 appropriately.

Specific examples of the sulfide solid electrolyte material include Li ₂ SP ₂ S ₅ , Li ₂ SP ₂ S ₅ -LiX (X is a halogen element), Li ₂ S-P2S5-Li ₂ O, Li ₂ SP ₂ S ₅ -Li ₂ O- Li ₂ S-SiS ₂ , Li ₂ S-SiS ₂ -LiI, Li ₂ S-SiS ₂ -LiBr, Li ₂ S-SiS ₂ -LiCl, Li ₂ S-SiS ₂ -B ₂ S ₃ -LiI, Li ₂ S-SiS ₂ -P ₂ S ₅ -LiI, Li ₂ SB ₂ S ₃ , Li ₂ S -P ₂ S ₅ -Z _m S _n (where m and n are positive numbers and Z is one of Ge, _{), Li 2 S-GeS 2} , Li 2 S-SiS 2 -Li 3 PO 4, Li 2 S-SiS 2 -Li p MO q (p, q is a positive number, M is p, Si, Ge, B, Al , Ga or In), and the like.

According to one embodiment, in the solid electrolyte 300, among the above-described sulfide solid electrolyte materials, those containing at least sulfur (S), phosphorus (P), and lithium (Li) can be used. Li ₂ SP ₂ S ₅ can be used.

In the case of using a material containing Li ₂ S-P ₂ S ₅ as a sulfide solid electrolyte material for forming the solid electrolyte 300, the mixing molar ratio of Li ₂ S and P ₂ S ₅ is, for example, Li ₂ S: P ₂ S ₅ = 50: 50 to 90: 10.

Examples of the shape of the solid electrolyte 300 include particle shapes such as a pseudo-spherical shape and an elliptic spherical shape. The average particle diameter of the solid electrolyte 300 may be 0.01 占 퐉 or more and 30 占 퐉 or less, and may be specifically 0.1 占 퐉 or more and 20 占 퐉 or less, for example. The average particle diameter, as described above, represents the number average diameter of the particle size distribution obtained by the scattering method or the like.

<4. Manufacturing Method of Lithium Ion Secondary Battery>

The configuration of the lithium ion secondary battery 1 according to the preferred embodiment of the present invention has been described in detail above. Next, a method of manufacturing the lithium ion secondary battery 1 having the above-described configuration will be described. The lithium ion secondary battery 1 can be manufactured by manufacturing the anode layer 10, the cathode layer 20, and the solid electrolyte layer 30, and then laminating these layers. Each step will be described in detail below.

(4.1 Preparation of positive electrode active material particles (11)

First, a method for producing the positive electrode active material particles 11 will be described. The method for producing the positive electrode active material particles 11 is not particularly limited and can be produced, for example, by the following production method.

Lithium carbonate (Li ₂ CO ₃ ) and cobalt oxide (Co ₃ O ₄ ) are mixed at a molar ratio of Li: Co = 1.00: 1.00 and then fired while blowing air. Here, the firing temperature is, for example, 950 占 폚, and the firing time is, for example, 4 hours. Thereby, the LCO particles 10a are produced. When the element M1 is dissolved in the LCO particles, a compound containing the element M1 may be further mixed and fired in a mixture of lithium carbonate (Li ₂ CO ₃ ) and cobalt oxide (Co ₃ O ₄ ). The compound containing the element M1 differs depending on the element M1. However, when the element M1 is magnesium, for example, magnesium hydroxide (Mg (OH) ₂ ) may be used.

Subsequently, lithium hydroxide (LiOH), nickel hydroxide (Ni (OH) ₂ ) and a compound containing element M1 are mixed at a desired molar ratio to prepare a mixed powder. Here, the compound containing the element M1 differs depending on the element M1, but when the element M1 is aluminum, aluminum hydroxide (Al (OH) ₃ ) may be used. If the molar ratio of the nickel atom to the element M1 in the cathode active material particle 11 is 95: 5, the lithium hydroxide (LiOH), the nickel hydroxide (Ni (OH) ₂ ) : 0.05.

The mixed powder and the LCO particles 11a are then mixed so that the molar ratio of the cobalt atoms in the cathode active material particles 11 to the total number of atoms of the nickel atoms and the element M1 is a desired molar ratio. Subsequently, this mixed powder is compounded using NOB-MINI (Hosokawa Micron). As a result, the precursor of the first coating layer 11b is carried on the surface of the LCO particles 11a. The precursor-coated LCO particles are then calcined while blowing oxygen. The firing temperature is, for example, 750 占 and the firing time is, for example, 4 hours. Thus, the positive electrode active material particles 11 are obtained.

The cathode active material particles 11 obtained in the above process have a particle size distribution. Thus, classification can be performed so that the average particle diameter of the cathode active material particles 11 becomes a desired value. The positive electrode active material particles 11 can be classified into an arbitrary average particle size by using, for example, a centrifugal force classifier (for example, a pico line made by Hosokawa Micron Corporation). The average particle diameter of the cathode active material particles 11 can be measured by a dry particle size distribution measuring apparatus (for example, Microtrack MT-3000II, Nikkiso Co., Ltd.). In the following examples, the average particle size was adjusted in this manner.

(4.2. The coating layer 12  Produce)

Next, a manufacturing method of the second coating layer 12 will be described. First, an alcohol solution (coating liquid) of lithium and element M2 is prepared by mixing lithium alkoxide and alkoxide of element M2 in an organic solvent such as alcohol, ethyl acetoacetate and a water. Here, the concentration of the alkoxide in the element M2 is determined so that the molar ratio of the element M2 to the total number of atoms of the total transition metal (for example, nickel atom and cobalt atom) in the cathode active material particle 11 is 10.0 mol% or less. The lower limit of the molar ratio of the element M2 is not particularly limited, but may be 0.1 mol%.

The lithium alkoxide and the alkoxide of the element M2 can be obtained by reacting an organic substance containing lithium and the element M2 (for example, organic lithium or the like) with an alcohol. The stirring mixing time is not particularly limited, but may be, for example, about 30 minutes. Further, a compound having a structure of CH3-CO-CH2-CO-OR such as ethyl acetoacetate has the effect of stabilizing an unstable metal by acting as a chelating agent in two carbonyl groups in the above structure. It will act as a stabilizer for the alkoxide.

Next, the coating liquid is mixed with the cathode active material particles 11 described above. Subsequently, while the mixed solution of the coating liquid and the cathode active material particles 11 was stirred, To evaporate all of the solvent such as alcohol. The evaporation of the solvent is carried out while irradiating the mixed solution with ultrasonic waves. This can support the precursor of the second coating layer 12 on the surface of the cathode active material particle 11.

Further, the precursor of the second coating layer 12 carried on the particle surface of the cathode active material particle 11 is fired. At this time, the firing temperature is 400? . The firing temperature may be lowered to less than 400 DEG C and the second coating layer 12 may be made amorphous. The baking time is not particularly limited and may be, for example, about 1 to 2 hours. The firing is carried out while blowing oxygen gas. By blowing oxygen gas, the reduction of nickel in the cathode material containing nickel can be suppressed and the capacity can be maintained. By the above process, the surface of the cathode active material particle 11 can be coated with the second coating layer 12. That is, the coated particles 10a can be produced. Further, in the case of manufacturing the anode layer 10 according to the modified example, the manufacturing process of the second coating layer 12 is omitted.

(4.3) Preparation of Solid Electrolyte Particle (31)

The production method of the solid electrolyte particles 31 is not particularly limited, and a usual method is optionally applicable. For example, the solid electrolyte particles 31 can be produced by a melt quenching method or a mechanical milling method (MM method). Hereinafter, a method for producing the solid electrolyte particles 31 including Li ₂ S and P ₂ S ₅ as an example of a method for producing the solid electrolyte particles 31 will be described.

In the case of the melt quenching method, for example, a predetermined amount of Li ₂ S and P ₂ S ₅ are mixed to form a pellet, which is reacted in a vacuum at a predetermined reaction temperature and quenched to obtain a sulfide-based solid electrolyte . The reaction temperature at this time may be, for example, 400 ° C to 1000 ° C, more specifically 800 ° C to 900 ° C. The reaction time may be, for example, 0.1 hour to 12 hours, more specifically 1 to 12 hours. The quenching temperature of the reactant may be generally 10 ° C or less, specifically 0 ° C or less, and the cooling rate may be usually about 1 to 10000 K / sec, specifically about 1 to 1000 K / sec.

In the case of the MM method, for example, a predetermined amount of Li ₂ S and P ₂ S ₅ are mixed and reacted for a predetermined time by mechanical milling to obtain a sulfide-based solid electrolyte. The mechanical milling method using the raw materials has an advantage that the reaction can be performed at room temperature. According to the MM method, since the solid electrolyte can be produced at room temperature, the solid electrolyte of the charged component can be obtained without pyrolysis of the raw material. The rotation speed and rotation time of the MM method are not particularly limited. However, the higher the rotation speed, the faster the production rate of the solid electrolyte, and the longer the rotation time, the higher the conversion rate of the raw material to the solid electrolyte.

Thereafter, the obtained solid electrolyte is subjected to heat treatment at a predetermined temperature and then pulverized to obtain solid electrolyte particles (31). The mixing ratio of the sulfides including Li ₂ S and P ₂ S ₅ is usually in the range of 50:50 to 80:20, specifically 60:40 to 75:25 in terms of molar ratio.

(4.4. The anode layer 10  Produce)

A mixture of the coated particles 10a (or the positive electrode active material particles 11), the solid electrolyte particles 31 and various additives is added to a solvent to prepare a slurry or paste-like positive electrode mixture. Here, the solvent is not particularly limited as long as it can be used for producing the positive electrode mixture, and for example, a non-polar solvent can be used. This is because the non-polar solvent is difficult to react with the solid electrolyte particles 31. Then, the obtained positive electrode mixture is applied to a current collector by using a doctor blade or the like and dried. Then, the current collector and the positive electrode material mixture layer are compacted with a rolling roll or the like to obtain the positive electrode layer 10.

The current collector that can be used in this case includes, for example, a plate or a thin body made of stainless steel, titanium, aluminum, an alloy thereof, or the like. Alternatively, the positive electrode layer 10 may be formed by compacting the positive electrode mixture in the form of a pellet without using a current collector.

(4.5. The cathode layer 20  Produce)

A method of manufacturing the cathode layer 20 is as follows. For example, a mixture of the negative electrode active material particles 21, the solid electrolyte particles 31 and various additives is added to a solvent to prepare a slurry or a paste-like negative electrode mixture. Here, the solvent is not particularly limited as long as it can be used in the production of the negative electrode mixture, and for example, a non-polar solvent may be used. This is because the non-polar solvent is difficult to react with the solid electrolyte particles 31. Then, the obtained negative electrode mixture is coated on a current collector by using a doctor blade or the like and dried. Then, the current collector and the negative electrode material mixture layer are compacted by a rolling roll or the like to obtain the negative electrode layer 20.

The current collector that can be used at this time may be, for example, a plate or a foil made of copper, stainless steel, nickel or an alloy thereof, or the like. Alternatively, the negative electrode layer 20 may be formed by compacting a mixture of the negative electrode active material particles 21 and various additives in a pellet form without using a current collector. When a metal or an alloy thereof is used as the negative electrode active material particles 21, the metal sheet (foil) may be used as it is.

(4.6 solids The thickness of the electrolyte layer 30  Produce)

A method for producing the solid electrolyte layer 30 is as follows. The solid electrolyte layer 30 is formed by forming the solid electrolyte particles 31 using a known film forming method such as blasting, aerosol deposition, cold spraying, sputtering, vapor deposition (CVD) Can be manufactured. Alternatively, a method may be employed in which a solution prepared by mixing the solid electrolyte particles 31 with a solvent and a binder (such as a binder and a polymer compound) is applied, and then the solvent is removed to form a film. It is also possible to reinforce the strength of the solid electrolyte particles 31 themselves or the solid electrolyte particles 31 and the binder (binder or polymer compound) or the support (solid electrolyte layer 30) And the like) and the like can be formed by pressing an electrolyte.

(4.7 lamination of each layer)

The lithium ion secondary cell 1 according to the present embodiment can be produced by laminating the anode layer 10, the solid electrolyte layer 30 and the cathode layer 20 obtained as described above in this order and pressing the same have.

[ Example ]

Next, an embodiment of the present embodiment will be described. Of course, the present invention is not limited to the following examples.

(One. Example  One)

(1.1 Preparation of positive electrode active material particle 11)

Lithium carbonate and cobalt oxide were mixed at a molar ratio of Li: Co = 1.00: 1.00 and then fired at 950 ° C for 4 hours while blowing air. Thus, LCO particles 11a were obtained. The average particle diameter of the LCO particles 11a was measured by the above-mentioned method, and the average particle diameter was 18 μm.

Next, a powder obtained by mixing lithium hydroxide, nickel hydroxide and aluminum hydroxide in a molar ratio of Li: Ni: Al = 1.00: 0.95: 0.05 was prepared. The mixed powder and the LCO particles 11a were mixed so that the molar ratio of cobalt atoms to nickel atoms and aluminum atoms was Co: (Ni + Al) = 0.95: 0.05.

Subsequently, the mixed powder was compounded by using NOB-MINI (Hosokawa microclone). As a result, the precursor of the first coating layer 11b (precursor of lithium-nickel-aluminum oxide) was supported on the surface of the LCO particles. This precursor was then calcined at 750 캜 for 4 hours while blowing oxygen. The positive electrode active material particles 11 were obtained by this firing. The composition of the positive electrode active material particle 11 was LiCo _0.95 (Ni _0.95 Al _0.05 ) _0.05 O ₂ . The average particle diameter of the cathode active material particles 11 was measured by the above-mentioned method, and the average particle diameter was 19 μm.

(1.2 Preparation of Solid Electrolyte Particles 31)

Li ₂ S and P ₂ S ₅ were mixed at a molar ratio of 80/20 by mechanical milling (MM treatment) to obtain solid electrolyte particles 31. The average particle diameter (D50) of the solid electrolyte particles 31 was 10 占 퐉. Here, the average particle diameter is the average particle diameter of the secondary particles of the solid electrolyte particles 31. The secondary particles were regarded as spherical when measuring the average particle diameter.

(1.3 Production of lithium ion secondary battery)

The lithium ion secondary battery 1 was produced by the following steps. Further, the following steps were all performed under an inert gas atmosphere. The positive electrode active material particles 11, the solid electrolyte particles 31, and the carbon black powder as the conductive agent were mixed at a mass ratio of 60/35/5 using a mortar until they became uniform. Thus, a positive electrode mixture was obtained. 30 mg of this positive electrode material mixture was inserted into a molding jig and press-molded at 2 ton / cm ² to form a positive electrode mixture. The positive electrode layer 10 was prepared by laminating a pelletized positive electrode mixture on a stainless steel current collector.

Subsequently, 100 mg of the solid electrolyte particles 31 were inserted into the molding jig and press-molded at 2 ton / cm ² to prepare the solid electrolyte layer 30. The positive electrode layer was inserted into the molding jig and press molded at 2 ton / cm ² to solidify the solid electrolyte layer 30 and the positive electrode layer 10.

Subsequently, 30.0 mg of graphite powder (vacuum-dried at 80 占 폚 for 24 hours) as a negative electrode mixture was inserted into the molding jig so that the solid electrolyte layer 30 was sandwiched between the anode layer 10 and the cathode layer 20, cm &lt; ^{2 &} gt ;. Thus, the solid electrolyte layer 30 and the cathode layer 20 were integrated. By the above steps, a test cell was obtained.

(1.4 cycle life test)

The obtained test cell was subjected to a constant current charge / discharge cycle test at a room temperature (25 DEG C) at 0.05C. Specifically, the charge / discharge cycle in which the test cell was charged at a constant current of 0.05 C at a temperature of 25 DEG C to the upper limit voltage of 4.2 V and discharging to the discharge end voltage of 2.5 V was repeated for 50 cycles. The ratio of the discharge capacity in the 50th cycle to the discharge capacity (initial capacity) in the first cycle was defined as the discharge capacity retention rate. The discharge capacity retention rate is a parameter showing the cycle characteristics. The larger the value, the better the cycle characteristics.

(2. Example  2)

A mixed powder of lithium hydroxide, nickel hydroxide and aluminum hydroxide and LCO particles 11a were mixed so that the total molar ratio of cobalt, nickel and aluminum became Co: (Ni + Al) = 0.90: 0.10. Except for this, the same treatment as in Example 1 was carried out. The average particle diameter of the positive electrode active material particles 11 was 20 占 퐉.

(3. Example  3)

The following process was carried out to prepare coated particles 11a, and the coated particles 11a were used to prepare test cells. Except for this, the same treatment as in Example 1 was carried out.

(3.1 Preparation of coated particles 10a)

A 10% solution of lithium methoxide methanol and zirconium (IV) propoxide were mixed in an isopropyl alcohol solution for 30 minutes to convert the zirconium (IV) propoxide to lithium Methoxide in methanol solution. Thus, a mixed solution was prepared. Then, the cathode active material particles 11 prepared in Example 1 were added to the mixed solution.

Here, the number of moles of the zirconium atom contained in the zirconium (IV) propoxide is n1, the total number of atoms (total number of moles) of the total transition metal (nickel and cobalt atoms in Example 3) in the positive electrode active material particles 11 is n2 The concentration of the mixed solution and the amount of the positive electrode active material particles 11 were adjusted so that the ratio of n1 and n2 (that is, the value of n1 / n2 * 100) was 0.5 mol%.

Then, the obtained mixed solution was heated to 40 캜 and stirred while evaporating all of the solvent. The evaporation of the solvent was carried out while irradiating ultrasonic waves to the mixed solution. Thus, the precursor of the second coating layer 12 (that is, the reaction precursor of the lithium-zirconium oxide) was supported on the surface of the positive electrode active material particle 11. The precursor of the lithium-zirconium oxide supported on the surface of the cathode active material particle 11 was fired at 350 DEG C for 1 hour while blowing oxygen. Thus, coated particles 10a according to Example 3 were obtained. The second coating layer 12 of Example 3 is composed of lithium-zirconium oxide. When the mole number of zirconium contained in the zirconium (IV) propoxide is n1 and the total number of atoms of the total transition metal in the positive electrode active material particles 11 is n2, the ratio of n1 and n2 is 0.5 mol%. The average particle diameter of the coated particles 10a was measured by the above-mentioned method, and the average particle diameter was 19 占 퐉.

Hereinafter, the molar number n1 of the element M2 (zirconium in the third embodiment) in the second coating layer 12 and the total number n2 of the total transition metal atoms (nickel atoms and cobalt atoms in the example 3) in the positive electrode active material particle 11 Is referred to as &quot; coating amount of the second coating layer 12 &quot;.

The HAADF-STEM image of the coating particle (10a) obtained in Example 3 is shown in Fig. 5 has a protective film formed on the second coating layer 12 (denoted by "Zr coating layer" in FIG. 5). In Fig. 5, the first coating layer 11b is denoted by &quot; NCA layer &quot;. As shown in FIG. 5, it can be seen that the first coating layer 11a and the second coating layer 12 are coated on the LCO particles 11a by the manufacturing method of the first and third embodiments. The coated particles 10a were observed with HAADF-STEM as a whole, and it was confirmed that the coated particles 10a were substantially spherical.

The element distribution in the thickness direction in Fig. 5 was measured by EELS (electron beam energy loss spectroscopy). The measuring device (Gatan 863GIF Tridiem) was used. As a result, the strength line profile shown in Fig. 6 was obtained. The horizontal axis in Fig. 6 represents the distance (depth) from the surface of the protective film to the measurement surface, and the vertical axis represents the area density (intensity) of each element on the measurement surface. As shown in Fig. 6, the surface density of the nickel atom becomes smaller as the distance from the surface of the coated particle 10a to the measurement surface becomes longer. On the other hand, the surface density of the cobalt atoms increases as the distance from the surface of the coated particles 10a to the measurement surface increases. This change occurs at the interface between the LCO particles 11a and the first coating layer 11b and in the vicinity thereof. This concentration gradient is presumed to occur when the precursor of the first coating layer 11b is baked. Namely, the nickel atoms in the precursor of the first coating layer 11b move into the LCO particles 11a by firing, and the cobalt atoms in the LCO particles 11a move into the precursors of the first coating layer 11b.

(4. Example  4)

Lithium hydroxide and nickel hydroxide were mixed at a molar ratio of Li: Ni = 1.0: 1.0. The mixed powder and the LCO particles (11a) were mixed so that the molar ratio of cobalt atoms to nickel atoms was Co: Ni = 0.95: 0.05. Other than that, the same treatment as in Example 3 was carried out. The average particle diameter of the positive electrode active material particles 11 was 18 占 퐉.

(5. Example  5)

Except that aluminum (Al) (III) propoxide was used in place of zirconium (IV) propoxide, coating particles (11a) were prepared in the same manner as in Example 3. The procedure of Example 3 was otherwise modified.

(6. Example  6)

The same treatment as in Example 3 was conducted except that a 10% solution of lithium methoxide methanol and a solution of lanthanum (La) (III) propoxide were mixed in a mixed solution of tetrahydrofuran and ethyl acetoacetate for 30 minutes.

(7. Example  7)

Except that yttrium (Y) (III) propoxide was used in place of zirconium (IV) propoxide, coating particles (11a) were prepared in the same manner as in Example 3. The procedure of Example 3 was otherwise modified.

(8. Example  8)

The same treatment as in Example 3 was conducted except that a 10% solution of lithium methoxide methanol and a solution of cerium (IV) propoxide were mixed in a mixed solution of tetrahydrofuran and ethyl acetoacetate for 30 minutes.

(9. Example  9)

Coating particles 11a were prepared in the same manner as in Example 3, except that gallium (Ga) (III) propoxide was used instead of zirconium (IV) propoxide. The procedure of Example 3 was otherwise modified.

(10. Example  10)

Coating particles 11a were prepared in the same manner as in Example 3 except that indium (In) (III) propoxide was used in place of zirconium (IV) propoxide. The procedure of Example 3 was otherwise modified.

(11. Example  11)

(11a) was prepared in the same manner as in Example 3, except that titanium (Ti) (IV) propoxide was used instead of zirconium (IV) propoxide. The procedure of Example 3 was otherwise modified.

(12. Example  12)

Except that niobium (Nb) (V) propoxide was used in place of zirconium (IV) propoxide, the coating particles 11a were prepared. The procedure of Example 3 was otherwise modified.

(13. Example  13)

The cathode active material particles 11 prepared in Example 1 were classified to prepare cathode active material particles 11 having an average particle diameter of 9.0 占 퐉. Except for this, the same treatment as in Example 1 was carried out.

(14. Example  14)

The cathode active material particles 11 produced in Example 1 were classified to prepare cathode active material particles 11 having an average particle diameter of 32 탆. Except for this, the same treatment as in Example 1 was carried out.

(15. Example  15)

The same process as in Example 1 was performed except that the cathode active material particles 11 were produced according to the following steps. First, lithium carbonate, cobalt oxide, and magnesium hydroxide were mixed at a molar ratio of Li: Co: Mg = 1.00: 0.99: 0.01, followed by firing at 950 ° C for 4 hours while blowing air. Thus, LCO particles 11a in which the magnesium atoms were dissolved were obtained. The magnesium atom corresponds to the element M1. The average particle diameter of the LCO particles 11a was measured by the aforementioned method, and the average particle diameter was 19 占 퐉.

Next, a powder obtained by mixing lithium hydroxide, nickel hydroxide and aluminum hydroxide in a molar ratio of Li: Ni: Al = 1.00: 0.95: 0.05 was prepared. (Co + Mg): (Ni + Al) = 0.95: 0.05 (molar ratio) of the total number of atoms of the cobalt atom and the magnesium atom to the total number of atoms of the nickel atom and the aluminum atom, .

Subsequently, the mixed powder was compounded by using NOB-MINI (Hosokawa microclone). As a result, the precursor of the first coating layer 11b (precursor of lithium-nickel-aluminum oxide) was supported on the surface of the LCO particles. This precursor was then calcined at 750 캜 for 4 hours while blowing oxygen. The positive electrode active material particles 11 were obtained by this firing. The composition of the positive electrode active material particle 11 was Li (Co _0.99 Mg _0.01 ) _0.95 (Ni _0.95 Al _0.05 ) _0.05 O ₂ . The average particle diameter of the cathode active material particles 11 was measured by the above-mentioned method, and the average particle diameter was 19 μm.

(16. Example  16)

Lithium hydroxide and nickel hydroxide were mixed at a molar ratio of Li: Ni = 1.0: 1.0. Then, the molar ratio of the total atom number of the cobalt atom and the magnesium atom to the atom number of the nickel atom was (Co + Mg): Ni = 0.95: 0.05. Other than that, the same treatment as in Example 15 was carried out. The average particle diameter of the positive electrode active material particles 11 was 21 탆.

(17. Example  17)

A mixed powder of lithium hydroxide, nickel hydroxide and aluminum hydroxide and LCO particles 11a were mixed so that the total molar ratio of cobalt, nickel and aluminum became Co: (Ni + Al) = 0.70: 0.30. Except for this, the same treatment as in Example 1 was carried out. The average particle diameter of the positive electrode active material particles 11 was 21 탆.

(18. Example  18)

The coating amount of the second coating layer 12 was set to 0.1 mol%, and the rest was treated in the same manner as in Example 3.

(19. Example  19)

The coating amount of the second coating layer 12 was adjusted to 10.0 mol%, and the rest was treated in the same manner as in Example 3.

(20. Example  20)

A mixture of lithium hydroxide, nickel hydroxide and manganese hydroxide in a molar ratio of Li: Ni: Mn = 1.00: 0.80: 0.20 was prepared. The mixed powder and the LCO particles 11a were mixed so that the total molar ratio of cobalt, nickel and manganese became Co: (Ni + Mn) = 0.95: 0.05. Except for this, the same treatment as in Example 1 was carried out. The average particle diameter of the positive electrode active material particles 11 was 20 占 퐉.

(21. Comparative Example  One)

The LCO particles (11a) prepared in Example 1 were used as the cathode active material particles (11), and the remainder was treated in the same manner as in Example 1.

(22. Comparative Example  2)

The same second coating layer 11b as in Example 3 was formed on the surface of the LCO particles 11a prepared in Example 1. [ A test cell was prepared using the coated particles thus prepared, and the remainder was treated in the same manner as in Example 1.

(23. Comparative Example  3)

NCM particles having an average particle diameter of 15 mu m were prepared and used as the cathode active material particles 11, and the remainder was treated in the same manner as in Example 1. [

(24. Comparative Example  4)

A mixed powder of lithium hydroxide, nickel hydroxide and aluminum hydroxide and LCO particles (11a) were mixed so that the molar ratio of cobalt and nickel to aluminum was Co: (Ni + Al) = 0.50: 0.50. Except for this, the same treatment as in Example 1 was carried out.

(25. Comparative Example  5)

The same treatment as in Example 3 was carried out except that the coating amount of the second coating layer 12 was 15.0 mol%.

(26. Comparative Example  6)

The cathode active material particles 11 prepared in Example 1 were classified to prepare cathode active material particles 11 having an average particle diameter of 3.0 占 퐉. Except for this, the same treatment as in Example 1 was carried out.

(27. Comparative Example  7)

The cathode active material particles 11 prepared in Example 1 were classified to prepare cathode active material particles 11 having an average particle diameter of 43.0 m. Except for this, the same treatment as in Example 1 was carried out.

The structures of the positive electrode active material particles 11 according to Examples 1 to 20 and Comparative Examples 1 to 7 are shown in Table 1, the composition of the second coating layer 12 is shown in Table 2, and the evaluations are shown in Table 3, respectively.

 [Table 1]

 [Table 2]

 [Table 3]

According to Tables 1 to 3, it was confirmed that Examples 1 to 20 having the cathode active material particles 11 or coated particles 10a of this embodiment had remarkably improved discharge capacity and cycle characteristics than Comparative Examples 1 to 7 .

That is, when comparing Examples 1 to 20 and Comparative Examples 1 and 2, it was found that the positive electrode active material particles 11 need to have at least the first coating layer 11b. Comparing Examples 1 to 20 and Comparative Examples 3 and 4, it was found that the composition of the cathode active material particle 11 had to satisfy the formula (1). In comparison between Examples 1 to 20 and Comparative Example 5, when the second coating layer 12 is formed on the surface of the positive electrode active material particles 11, the coating amount thereof should be 10.0 mol% or less. Comparing Examples 1 to 20 and Comparative Examples 6 and 7, it was found that the average particle size of the cathode active material particles 11 was required to be 5 to 35 μm.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to these examples. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. .

One… Lithium ion secondary battery
10 ... Anode layer
10a ... Coated particle
11 ... Cathode active material particle
11a ... LCO particles
11b ... The first coating layer
12 ... The second coating layer
20 ... Cathode layer
21 ... Anode active material particle
30 ... Electrolyte layer
31 ... Solid electrolyte particles

Claims (15)

A lithium ion secondary battery comprising: a positive electrode including a positive electrode active material particle and solid electrolyte particles contacting the positive electrode active material particle,
The positive electrode active material particles,
Lithium cobalt oxide particles;
A first coating layer containing a nickel atom and covering at least a part of the lithium cobalt oxide particles; And
Ba, Mg, Al, Si, Sc, Ti, V, Cr, Mn, Fe, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, In, Sn, Sb, La, At least one element M1 selected from the group consisting of Tb, Hf, Ta and Pb;
Lithium ion secondary battery. The method according to claim 1,
Wherein the first coating layer further comprises at least one element selected from the group consisting of a lithium atom, an oxygen atom and the same element as the element M1. The method according to claim 1,
Wherein the total composition of the positive electrode active material particles is represented by the following Formula 1:
[Chemical Formula 1]
Li _x Ni _y Co _z M1 _{1- y z} O ₂
In the above formula (1)
M1 is the element M1, and x, y, and z are values satisfying 0.5 <x <1.2, 0 <y <0.4, z> 0.6, and y + z? 1.0. The method according to claim 1,
Wherein the average particle diameter of the positive electrode active material particles is 5 to 35 占 퐉. The method according to claim 1,
Wherein the element M1 is at least one element selected from the group consisting of Mg, Al and Mn. The method according to claim 1,
Wherein the molar ratio of the nickel atoms and the cobalt atoms in the positive electrode active material particles continuously changes from the surface of the positive electrode active material particles toward the center thereof. The method according to claim 1,
And the element M1 is contained in the lithium cobalt oxide particles. The method according to claim 1,
Wherein the cathode active material particle further comprises a second coating layer covering at least a part of the first coating layer,
The second coating layer may be formed of at least one selected from the group consisting of B, Mg, Al, Si, Sc, Ti, V, Cr, Mn, Fe, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, In, Sn, , Pr, Eu, Tb, Hf, Ta, and Pb. 9. The method of claim 8,
Wherein the molar ratio of the element M2 to the total number of atoms of the total transition metals in the positive electrode active material particles is 10.0 mol% or less. 9. The method of claim 8,
Wherein the element M2 is at least one element selected from the group consisting of Al, Ti, Ga, Y, Zr, Nb, In, La and Ce. The method according to claim 1,
Wherein the positive electrode active material particles are spherical. The method according to claim 1,
Wherein the solid electrolyte particle is a sulfide-based solid electrolyte particle. 13. The method of claim 12,
Wherein the sulfide solid electrolyte comprises at least sulfur and lithium,
At least one element selected from phosphorus (P), silicon (Si), boron (B), aluminum (Al), germanium (Ge), zinc (Zn), gallium (Ga) A lithium ion secondary battery. 13. The method of claim 12,
The sulfide solid electrolyte may be lithium sulfide; And at least one selected from silicon sulfide, phosphorus sulfide, and boron sulfide. 13. The method of claim 12,
Wherein said sulfide solid electrolyte comprises Li ₂ S and P ₂ S ₅ .

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